Silicon germanium (SiGe) heterojunction bipolar transistors are employed in an increasing number of integrated circuit applications. Development of silicon germanium (SiGe) heterojunction bipolar transistor technology has been very rapid since the first functional silicon germanium (SiGe) heterojunction bipolar transistor was introduced in December 1987. The first silicon germanium (SiGe) heterojunction bipolar transistor technology entered commercial production on 200-mm wafers in 1994.
The technical advantages that are provided by silicon germanium (SiGe) heterojunction bipolar transistor technology continue to be investigated by researchers in the semiconductor industry. There continues to be a need in the art for systems and methods that provide improvements in silicon germanium (SiGe) heterojunction bipolar transistor technology.
The system and method of the present invention provides a self aligned silicon germanium (SiGe) heterojunction bipolar transistor that has an improved polyemit module. The polyemit module of the transistor of the present invention is formed using a double layer deposition process. In the double layer deposition process, the first layer is a layer of emitter polysilicon and the second layer is a sacrificial layer of silicon germanium (SiGe). The shape and thickness of the polysilicon layer of the polyemit module provides (1) a reduction in the overall resistance of the emitter and (2) an increase in the contact area between the emitter polysilicon layer and a contact structure that is more than three times the contact area that is provided in prior art polyemit modules.
Before undertaking the Detailed Description of the Invention below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like.
Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior uses, as well as to future uses, of such defined words and phrases.